Modeling Stream Temperature in the Anthropocene: An Earth System Modeling Approach

Summary

Stream temperature is a key determinant of aquatic ecosystem production and survival but also influences coal-fired energy production. However, it is generally not represented in Earth system models so its potentially large-scale impacts on aquatic ecosystem and coastal and ocean in coupled simulations are unknown. To fill this gap in modeling the water-energy nexus and terrestrial-aquatic interactions, Department of Energy scientists at Pacific Northwest National Laboratory (PNNL) developed a new stream temperature module in the Model for Scale Adaptive River Transport (MOSART) coupled with a generic water management model in the framework of the Community Earth System Model (CESM). The coupled models allow the impacts of reservoir operations and withdrawals on stream temperature to be explicitly represented in a physically based and consistent way. The models have been applied to the contiguous United States driven by observed meteorological forcing. The researchers found that the model is capable of reproducing stream temperature spatio-temporal variation satisfactorily when compared against the observed streamflow from over 320 USGS stations. Including water management in the model improves the agreement between the simulated and observed streamflow at a large number of stream gauge stations. They found that both climate and water management have an important influence on the spatio-temporal patterns of stream temperature. Furthermore, reservoir operation is estimated to cool the stream temperature in the summer low-flow season (August – October) by as much as 1~2oC by mitigating low-flow conditions, which has important implications to aquatic ecosystems. This work laid a solid foundation for future studies on terrestrial-aquatic interactions and the water-energy nexus.

Acknowledgments

This work was supported by the Office of Science of the U.S. Department of Energy Biological and Environmental Research as part of the Integrated Assessment Research Program. Initial model development and compilation of observation data for model evaluation were supported by the Platform for Regional Integrated Modeling and Analysis (PRIMA) initiative at the Pacific Northwest National Laboratory. The Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy under Contract DE-AC05-76RLO1830. The data and source code used in this study are available upon individual request (hongyi.li@pnnl.gov).